Storage tanks for liquefied hydrocarbon products such as butane and propane present special problems for the safe and ready monitoring of tank volume levels. This is particularly so where the tanks are located in remote or relatively inaccessible locations, making tank inspections inefficient and inconvenient.
Liquid Propane (“LP”) gas storage tanks are classified as explosion hazards by the National Fire Protection Association, requiring special care in the design and installation of any ancillary equipment. The LP Gas Code (NFPA 58) defines the area within 5 feet of any tank, fill opening or point where LP gas is dispensed, loaded, vented or the like as a Class I, Division 1, Group D hazard.
Despite the daunting nature of the problems involved in safely installing a volume monitor for such a tank, it would be desirable to provide a system and method for remotely reading volume levels so that fuel supplies can be accurately maintained in adequate amounts without the necessity of site trips to ascertain the amount of fuel on hand.
It is known in the measuring art to determine the weight of liquid contents in a tank by suspending a buoyant probe in the liquid from a load cell to measure the apparent weight of the probe. Examples of such systems in the prior patent art may be found in U.S. Pat. Nos. 5,614,672, 5,157,968, 5,132,923, and 4,244,218.
U.S. Pat. No. 5,157,968 discloses a buoyant displacement probe mounted through a top tank port via a load cell for the determination of the liquid tank content weight. It also provides a second buoyant probe mounted via a load cell through a second tank port, so that the specific gravity of the liquid may be calculated from the second load cell reading and the content weight can thus be converted to a volume. U.S. Pat. No. 5,614,672 likewise determines content weight by a load cell-mounted buoyant displacement probe. It, however, relies for volume determination on an assumption that the specific gravity of the liquid in the tank is a constant, known value.
Despite these efforts to provide tank monitors employing buoyant displacement probes for monitoring tank contents, there remains a lack of a suitable system and method for accurately and efficiently reading, monitoring and storing in-tank readings from a remote location. Accordingly, there is a need for a system and method that provides the ability to remotely monitor and track information about a storage tank from a remote location.